Screen printing device and screen printing method

ABSTRACT

Prior to a mark imaging process executed for the purpose of detecting a position of recognition marks for positioning the substrate and the mask, an optical axis calibration processing process of detecting a horizontal relative position between imaging optical axes, and a surface correction data creation processing process of detecting a local positional deviation of the imaging optical axes, which is caused by the travel of the imaging unit, are executed. Before starting production, a production pre-start precision evaluation process for evaluating a substrate positioning precision is executed by using a verification substrate and a verification mask, and after starting the production, a production post-start precision evaluation process for evaluating a substrate positioning precision after starting the production is executed by using a commercial production substrate and a commercial production mask.

TECHNICAL FIELD

The present invention relates to a screen printing device and a screenprinting method for printing a paste such as a solder cream on asubstrate.

BACKGROUND ART

As a method for supplying a component joint paste such as a solder creamonto a substrate in a component mount line where an electronic componentis mounted on the substrate, screen printing is used. In the screenprinting, the substrate is abutted against a mask plate in which patternholes are formed in correspondence with a print portion of the paste,and the paste is supplied onto the mask plate to conduct squeegeeingoperation of sliding a squeegee, to print the paste on the substratethrough the pattern holes. In order to property print the paste in thescreen printing, there is a need to property position the substrate withrespect to the mask plate.

The substrate positioning is generally conducted by imaging recognitionmarks each provided on the substrate and the mask plate by a camera toconduct positional recognition. In this situation, because a coordinatesystem when imaging the substrate and a coordinate system when imagingthe mask plate are different in position reference from each other,there is a need to obtain position reference data for specifying apositional relationship between those coordinate systems. For thatreason, up to now, a screen printing device has been known which includea calibration processing function of imaging the substrate and the maskplate to obtain the position reference data between the coordinatesystems (for example, refer to Patent Document 1). The related art inthe Patent Document describes an example in which, in a configurationwhere the mask plate and the substrate are imaged by a single imagingunit, a positional deviation between a coordinate system of a substratepositioning unit and a coordinate system of a moving unit for moving theimaging unit is obtained on the basis of image data acquired by theimaging unit.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-B-4364333

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

Incidentally, as a configuration of an imaging unit that images theabove-described substrate and mask plate for positional recognition,there is used a configuration having two imaging optical axes of anupward imaging optical axis having a lower surface of the mask plate asan imaging image, and a downward imaging optical axis having an uppersurface of the substrate as the imaging image. This configuration hassuch an advantage that the imaging unit is moved by a single travel unitto enable both of the substrate and the mask plate to be imaged.However, in conducting the positional recognition of the substrate andthe mask plate by the imaging unit thus configured, the above-describedconfiguration causes disadvantages described below in a case where theposition recognition is intended for a substrate requiring a highprinting position precision.

First, in a configuration having two imaging optical axes for imagingobjects in an upper direction and a lower direction, an error in somedegree unavoidably occurs in a directional position of an imagingoptical axis in processing of installing an optical system configuringthe imaging unit. For that reason, in an imaging operation for movingthe imaging unit to image the objects in the two upper and lowerdirections, when the imaging surface of the upper mask plate and theimaging surface of the lower substrate are to be imaged, an error occursin a horizontal direction of the two imaging optical axes, and a correctposition recognition result is not obtained. Further, ball screws usedfor a moving mechanism for horizontally moving the imaging unit withrespect to the substrate and the mask plate have a local position error,and a positional deviation specific to a target position to be moved ispresent between a command position indicated by a control command and amoved position to which the imaging unit is really moved.

For that reason, when plural types of substrates different in shape andsize are to be worked by an identical device, an error occurs in aposition recognition result according to a position of the substrate atwhich the recognition mark is formed. Also, since the recognition markon the mask plate corresponds to the position of the recognition mark onthe substrate, the same error occurs in the positional recognitionresult. When the substrate and the mask plate are positioned with theabove errors of the positional recognition results, the pattern holes donot precisely match the print portion of the substrate, resulting in aprinting trouble such as a printing positional deviation.

Further, complicated operation and processing such as adjustment of amachine parameter are required in calibration processing for confirminga precision in the positioning of the substrate and the mask plate.Therefore, up to now, the confirmation of the substrate positioningprecision is usually conducted only at a shipping inspection in a devicemanufacturer. For this reason, even when the user needs to confirmwhether the substrate positioning precision is high, or not, accordingto a requirement of printing quality management in productioncontinuation processing for executing printing on a plurality ofsubstrates, it is difficult to confirm the substrate positioningprecision in a simple method, and an appropriate countermeasure isdesired.

Under the circumstances, in order to attend to various problems with theabove-described related art, an object of the present invention is toprovide a screen printing device and a screen printing method, which caneasily confirm whether the substrate positioning precision is high, ornot, during the production continuation processing, in a configurationwhere the imaging unit having two imaging optical axes and intended toimage the substrate and the mask plate is horizontally moved.

Means for Solving the Problem

The present invention provides a screen printing device that abuts asubstrate against a mask plate in which pattern holes are formed toprint a paste, the screen printing device comprising: a substratepositioning unit that holds a substrate carried from an upstream side,and moves the substrate relatively in a horizontal direction and avertical direction to position the substrate at a given position; ascreen print unit that allows a squeegee to slide on the mask plate ontowhich the paste is supplied, to print the paste on the substrate throughthe pattern holes; an imaging unit that has two imaging optical axes ofwhich imaging directions are upward and downward, respectively, andconducts mark imaging operation of imaging a substrate recognition markand a mask recognition mark formed on the substrate and the mask plate,respectively; an imaging unit moving mechanism that moves the imagingunit in the horizontal direction with respect to the substrate and themask plate; a recognition processing unit that subjects an imagingresult in the mark imaging operation to recognition processing, therebyconducting mark recognition processing for detecting positions of thesubstrate recognition mark and the mask recognition mark; an opticalaxis calibration processing unit that detects relative positions of theimaging optical axes on a mask lower surface and a substrate uppersurface which are imaging surfaces of the two imaging optical axes,respectively, by imaging two reference marks associated with therelative positions by the imaging unit, individually, and outputs thedetected relative positions as inter-optical-axis relative positiondata; a surface correction data creation processing unit that obtains aposition error of the imaging optical axis occurring on the imagingsurfaces in the horizontal direction caused by the move of the imagingunit by the imaging unit moving mechanism, as a positional deviation inthe horizontal direction which is specific to each of reference pointsset in an ordered array for a substrate area on which the substrate isheld and a mask area on which a mask plate is installed, respectively,and outputs the obtained position error as surface correction datarepresenting a local positional deviation state in each of surfaces ofthe substrate area and the mask area; a substrate positioning controlunit that controls the imaging unit, the imaging unit moving mechanism,and the recognition processing unit so as to execute the mark imagingoperation and the mark recognition processing, and controls thesubstrate positioning unit on the basis of the inter-optical-axisrelative position data, the surface correction data, and the result ofthe mark recognition processing to execute substrate positioningoperation for positioning the substrate and the mask plate; and aprecision evaluation unit that evaluates a positioning precision of thesubstrate positioning operation, wherein the precision evaluation unitcorrects the moving operation of the imaging unit by the imaging unitmoving mechanism on the basis of the inter-optical-axis relativeposition data and the surface correction data for a commercialproduction substrate and a commercial production mask to execute themark imaging operation, the mark recognition processing, and thesubstrate positioning operation, and wherein after the substratepositioning operation, the precision evaluation unit further correctsthe moving operation of the imaging unit by the imaging unit movingmechanism on the basis of the inter-optical-axis relative position dataand the surface correction data to again execute the mark imagingoperation and the mark recognition processing, and evaluates thepositioning precision on the basis of the recognition result in the markrecognition processing.

The present invention also provides a screen printing method in which asubstrate is abutted against a mask plate having pattern holes formedtherein to print a paste, the screen printing method comprising: asubstrate holding step of holding a substrate carried from an upstreamside by a substrate positioning unit; a mark imaging step of imaging asubstrate recognition mark formed on the substrate, and a maskrecognition mark formed on the mask plate installed in a screen printingunit by an imaging unit that has two imaging optical axes of whichimaging directions are upward and downward, respectively, and is movedin a horizontal direction with respect to the substrate and the maskplate by the imaging unit moving mechanism; a mark recognitionprocessing step of recognizing an imaging result in the mark imagingstep by a recognition processing unit, thereby detecting positions ofthe substrate recognition mark and the mask recognition mark; asubstrate positioning step of positioning the substrate to the maskplate by controlling the substrate positioning unit on the basis of theposition detection results of the substrate recognition mark and themask recognition mark; and a screen printing step of printing a paste onthe substrate through the pattern holes by sliding a squeegee on themask plate having the pattern holes to which the paste is supplied,wherein, prior to the mark imaging step, there are executed: an opticalaxis calibration processing step of detecting horizontal relativepositions of the respective imaging optical axes on a mask lower surfaceand a substrate upper surface which are imaging surfaces of the twoimaging optical axes, respectively, by imaging two reference marksassociated with the relative positions, individually, and outputting thedetected relative positions as inter-optical-axis relative positiondata; and a surface correction data creation processing step ofobtaining a position error of the imaging optical axis occurring on theimaging surface in the horizontal direction caused by the move of theimaging unit by the imaging unit moving mechanism, as a positionaldeviation in the horizontal direction for each of reference points setin an ordered array for a substrate area on which the substrate is heldand a mask area on which a mask plate is installed, respectively, andoutputting the obtained position error as surface correction datarepresenting a local positional deviation state in each of surfaces ofthe substrate area and the mask area, wherein in a production post-startprecision evaluation step that is executed for evaluating a positioningprecision in a substrate positioning operation, the moving operation ofthe imaging unit by the imaging unit moving mechanism is corrected onthe basis of the inter-optical-axis relative position data and thesurface correction data for a commercial production substrate and acommercial production mask to execute the mark imaging step, the markrecognition processing step, and the substrate positioning step, andwherein after the substrate positioning step, the moving operation ofthe imaging unit by the imaging unit moving mechanism is corrected onthe basis of the inter-optical-axis relative position data and thesurface correction data to again execute the mark imaging step and themark recognition processing step, and the positioning precision isevaluated on the basis of the recognition result in the mark recognitionprocessing step.

Advantages of the Invention

According to the present invention, prior to the mark imaging that isobtained by imaging the substrate recognition mark formed on thesubstrate and the mask recognition mark formed on the mask plate by theimaging unit having two imaging optical axes, there are executed theoptical axis calibration processing step of imaging the two referencemarks associated with the relative positions by the imaging unit,individually, to detect the reference marks, and outputting thereference marks as the inter-optical-axis relative position data, andthe surface correction data creation processing step of obtaining theposition error of the imaging optical axis occurring on the imagingsurface in the horizontal direction caused by the move of the imagingunit by the imaging unit moving mechanism, as a positional deviation inthe horizontal direction for each of the reference points set in theordered array for the substrate area and the mask area, respectively,and outputting the obtained position error as the surface correctiondata representing the local positional deviation state in respectiveplanes of the substrate area and the mask area. With the aboveconfiguration, in order to correct the error of the horizontal relativeposition of the imaging optical axis in the mark imaging process, and toevaluate the positioning precision in the substrate positioningoperation, the precision evaluation process is executed for thesubstrate and the mask plate for the commercial production. This makesit possible to easily confirm whether the substrate positioningprecision is high, or not, during the production continuationprocessing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a screen printing device according to anembodiment of the present invention.

FIG. 2 is a front view of a screen printing device according to theembodiment of the present invention.

FIG. 3 is a plan view of a screen printing device according to theembodiment of the present invention.

FIGS. 4( a), 4(b), 4(c), and 4(d) are illustrative views of theoperation of the screen printing device according to the embodiment ofthe present invention.

FIGS. 5( a) and 5(b) are illustrative views of positioning of asubstrate and a mask plate in the screen printing device according tothe embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of a controlsystem in the screen printing device according to the embodiment of thepresent invention.

FIG. 7 is a flowchart illustrating working processing in a screenprinting method according to the embodiment of the present invention.

FIG. 8 is a flowchart illustrating optical axis calibration processingin the screen printing method according to the embodiment of the presentinvention.

FIG. 9 is a flowchart illustrating surface correction data creationprocessing in the screen printing method according to the embodiment ofthe present invention.

FIG. 10 is a flowchart illustrating production pre-start precisionevaluation processing in the screen printing method according to theembodiment of the present invention.

FIG. 11 is a flowchart illustrating production post-start precisionevaluation processing in the screen printing method according to theembodiment of the present invention.

FIGS. 12( a) to 12(e) are illustrative views of processes of opticalaxis calibration processing in the screen printing method according tothe embodiment of the present invention.

FIGS. 13( a) to 13(c) are illustrative views of processes of the opticalaxis calibration processing in the screen printing method according tothe embodiment of the present invention.

FIGS. 14( a) and 14(b) are diagrams illustrating a glass substrate and ajig mask for calibration used in the surface correction data creationprocessing in the screen printing method according to the embodiment ofthe present invention.

FIGS. 15( a) to 15(c) are illustrative views of processes of the surfacecorrection data creation processing in the screen printing methodaccording to the embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Subsequently, embodiments of the present invention will be describedwith reference to the drawings. First, a structure of a screen printingdevice will be described with reference to FIGS. 1, 2, and 3. Referringto FIG. 1, the screen printing device is configured to arrange a screenprinting unit 11 above a substrate positioning unit 1. The substratepositioning unit 1 has a function of holding a substrate carried in froman upstream side, moving the substrate in a horizontal direction and avertical direction, and positioning the substrate at a given position.The substrate positioning unit 1 is configured to stack a Y-axis table2, an X-axis table 3, and a O-axis table 4, and further combine a firstZ-axis table 5 and a second Z-axis table 6 thereon.

A configuration of the first Z-axis table 5 will be described. On anupper surface side of a horizontal base plate 4 a disposed on an uppersurface of the O-axis table 4, a horizontal base plate 5 a that issimilarly horizontal is up/down movably held by an elevating guidemechanism (not shown). The horizontal base plate 5 a is moved up anddown by a Z-axis elevator mechanism that is configured to rotationallydrive a plurality of feed screws 5 c through a belt 5 d by a motor 5 b.

A vertical frame 5 e is erected on the horizontal base plate 5 a, and asubstrate transport mechanism 8 is held on an upper end portion of thevertical frame 5 e. The substrate transport mechanism 8 has twotransport rails which are arranged in parallel to a substrate transportdirection (X-direction which is a direction perpendicular to a paperplane in FIG. 1). The substrate transport mechanism 8 transports asubstrate 10 to be printed while supporting both ends of the substrate10 by those transport rails. The substrate 10 that is held by thesubstrate transport mechanism 8 can be moved up and down together withthe substrate transport mechanism 8 with respect to a screen print unitwhich will be described later, by driving the first Z-axis table 5. Asillustrated in FIGS. 2 and 3, the substrate transport mechanism 8extends to an upstream side (left side in FIGS. 2 and 3) and adownstream side, and the substrate 10 carried in from the upstream sideis transported by the substrate transport mechanism 8, and furtherpositioned by the substrate positioning unit 1. Then, the substrate 10that has been printed by the screen printing unit 11 which will bedescribed later is transported to the downstream side by the substratetransport mechanism 8.

A configuration of the second Z-axis table 6 will be described. Ahorizontal base plate 6 a is up/down movably arranged along an elevatorguide mechanism (not shown) in between the substrate transport mechanism8 and the horizontal base plate 5 a. The base plate 6 a is moved up anddown by the Z-axis elevator mechanism that is configured to rotationallydrive a plurality of feed screws 6 c through a belt 6 d by a motor 6 b.A substrate lower receiving unit 7 having a lower receiving surface forholding the substrate 10 on an upper surface thereof is disposed on anupper surface of the horizontal base plate 6 a.

The substrate lower receiving unit 7 is moved up and down with respectto the substrate 10 which is held by the substrate transport mechanism 8by driving the second Z-axis table 6. Then, the lower receiving surfaceof the substrate lower receiving unit 7 is abutted against a lowersurface of the substrate whereby the substrate lower receiving unit 7supports the substrate 10 from the lower surface side. A damp mechanism9 is arranged on an upper surface of the substrate transport mechanism8. The damp mechanism 9 has two damp members 9 a arranged tohorizontally face each other, and one of the damp members 9 a is movedforward and backward by a drive mechanism 9 b to clamp and fix thesubstrate 10 from both sides thereof.

Subsequently, the screen printing unit 11 arranged above the substratepositioning unit 1 will be described. The screen printing unit 11 has afunction of sliding a squeegee on the mask plate to which the past hasbeen supplied, to thereby print the paste on the substrate through thepattern holes. Referring to FIGS. 1 and 2, a mask plate 12 is extendedon a mask frame 12 a, and pattern holes 12 b are formed in the maskplate 12 in correspondence with the shape and position (refer to FIG. 3)of an electrode 10 a to be printed on the substrate 10. A squeegee head13 is arranged on the mask plate 12. In the squeegee head 13, a squeegeeelevator mechanism 15 that moves up and down a squeegee 16 is arrangedon a horizontal plate 14. The squeegee 16 is moved up and down bydriving the squeegee elevator mechanism 15, and abutted against an uppersurface of the mask plate 12.

As illustrated in FIG. 2, guide rails 27 are arranged in a Y-directionon brackets 26 arranged on a vertical frame 25, and sliders 28 that areslidably fitted to the respective guide rails 27 are coupled to bothends of the horizontal plate 14. As a result, the squeegee head 13 isslidable in the Y-direction. The horizontal plate 14 is horizontallymoved in the Y-direction by a squeegee moving unit including a nut 30, afeed screw 29, and a squeegee moving motor (not shown) that rotationallydrives the feed screw 29. Guide rails 31 are arranged on the verticalframe 25 in the Y-direction, and sliders 32 that are slidably fitted tothe guide rails 31 are coupled to a head X-axis table 19 throughbrackets 19 a. With the above configuration, the head X-axis table 19 isslidable in the Y-axis.

As illustrated in FIG. 3, the head X-axis table 19 is coupled with animaging unit 17 that images the substrate 10 and the mask plate 12, anda cleaning mechanism 18 that cleans a lower surface of the mask plate12. As illustrated in FIG. 1, the imaging unit 17 is configured tointegrate a substrate recognition camera 17 a that images the substrate10, and a mask recognition camera 17 b that images the mask plate 12together. Also, as illustrated in FIG. 3, the cleaning mechanism 18 isconfigured to arrange a paper roll 18 b where an unused cleaning paperis wound on a horizontal unit base 18 a, a paper roll 18 c on which aused cleaning paper is wound, and a cleaning head 18 d that pushes thecleaning paper against a lower surface of the mask plate 12. Thecleaning paper drawn out of the paper roll 18 b is collected to thepaper roll 18 c through the cleaning head 18 d.

The head X-axis table 19 is horizontally moved in the Y-direction by ahead Y-axis moving mechanism 20 including a nut 34, a feed screw 33, anda head moving motor (not shown) that rotationally drives the feed screw33. The imaging unit 17 and the cleaning mechanism 18 are horizontallymoved in the X-direction and the Y-direction by driving the head X-axistable 19 and the head Y-axis moving mechanism 20, respectively. As aresult, imaging on the mask plate 12 at an arbitrary position, and anoverall area of a lower surface of the mask plate 12 can be cleaned. Thehead X-axis table 19 and the head Y-axis moving mechanism 20 configurean imaging unit moving mechanism 21 that moves the imaging unit 17 withrespect to the substrate 10 and the mask plate 12 in the horizontaldirection.

Subsequently, the print operation of the screen printing unit 11 will bedescribed. First, when the substrate 10 is carried in at a printposition by the substrate transport mechanism 8, the substrate lowerreceiving unit 7 is moved up by driving the second Z-axis table 6 toreceive the lower surface of the substrate 10 from the bottom. Then, inthis state, the substrate 10 is positioned with respect to the maskplate 12 by driving the substrate positioning unit 1. Thereafter, thesubstrate 10 is moved up together with the substrate transport mechanism8 by driving the first Z-axis table 5, and abutted against the lowersurface of the mask plate 12. Then, the substrate 10 is clamped by thedamp mechanism 9. With this operation, in the squeegeeing of thesqueegee head 13, a horizontal position of the substrate 10 is fixed.Then, in this state, the squeegee 16 is slid on the mask plate 12 ontowhich a solder cream that is a paste is supplied with the result thatthe solder cream is printed on the substrate 10 through the patternholes 12 b.

Subsequently, the configuration and the function of the imaging unit 17will be described with reference to FIGS. 4( a), 4(b), 4(c), and 4(d).As illustrated in FIG. 4( a), the imaging unit 17 coupled to the headX-axis table 19 is configured to arrange the mask recognition camera 17b having an upward imaging optical axis a2, and the substraterecognition camera 17 a having a downward imaging optical axis a1 alongthe head X-axis table 19 in parallel to the Y-direction in a planarview. The respective imaging holes input from the directions of theimaging optical axes a1 and a2 are guided by an optical system 17 c, andinput to the substrate recognition camera 17 a and the mask recognitioncamera 17 b. With this operation, a substrate recognition mark formed onthe substrate 10 and a mask recognition mark formed on the mask plate 12are imaged. Then, the positioning operation of precisely aligning therelative positions of the substrate 10 and the mask plate 12 is executedon the basis of the position detection results of the substraterecognition mark and the mask recognition mark which are acquired bysubjecting those imaging results to recognition processing.

That is, the imaging unit 17 is moved by the imaging unit movingmechanism 21, and has the two imaging optical axes a1 and a2 whoseimaging directions are downward and upward, respectively. The imagingunit 17 conducts the mark imaging operation of imaging the substraterecognition mark and the mask recognition mark formed on the substrate10 and the mask plate 12, respectively. In this embodiment, the imagingunit 17 is configured to arrange the two imaging cameras having posturesin which the imaging surfaces are oriented in opposite verticaldirections, that is, the substrate recognition camera 17 a and the maskrecognition camera 17 b in parallel in a plan view. The imaging unit 17does not always need to provide two imaging cameras, but as illustratedin FIG. 4( b), the imaging unit 17 may be configured to include a singleimaging camera 17 d having the two imaging optical axes a1 and a2 whoserespective imaging directions are downward and upward.

In the mark imaging operation of the imaging unit 17, as illustrated inFIG. 4( c), the imaging unit 17 and the cleaning mechanism 18 areintegrally moved into between the substrate 10 held by the substratepositioning unit 1, and the mask plate 12 (arrow b). Then, in thisstate, the lower substrate 10 is imaged by the substrate recognitioncamera 17 a whereas the upper mask plate 12 is imaged by the maskrecognition camera 17 b. In the imaging by the substrate recognitioncamera 17 a and the mask recognition camera 17 b, which are intended toposition the substrate 10 and the mask plate 12 as described above, arelative positional relationship in an optical coordinate system betweenthe two imaging cameras, in other words, a relative distance of theimaging optical axes on the respective imaging surfaces is required tobe a specific dimension represented by a design dimension in advance.

However, both of the imaging optical axes a1 and a2 are not alwaysprecisely oriented in a vertical direction. An optical axis errorspecific to the substrate recognition camera 17 a and the maskrecognition camera 17 b, or an error of the mount posture of thesubstrate recognition camera 17 a and the mask recognition camera 17 bmay cause the imaging optical axes a1 and a2 to be slightly inclinedfrom an accurate vertical direction, as illustrated in FIG. 4( d).Because of the above causes, the relative distance of the two imagingoptical axes a1 and a2 of the substrate recognition camera 17 a and themask recognition camera 17 b on the respective imaging surfaces becomesa relative distance D* which is different from a specified dimension Drepresented by the design dimension. That is, the relative distance D*between an imaging point P1 representing a position of the imagingoptical axis a1 on the upper surface of the substrate 10, and an imagingpoint P2 representing a position of the imaging optical axis a2 on thelower surface of the mask plate 12 becomes an inter-optical-axisrelative position data representing the relative positional relationshipof the respective coordinate systems of the substrate recognition camera17 a and the mask recognition camera 17 b. In this embodiment, for thepurpose of positioning the substrate 10 and the mask plate 12 with highprecision, the inter-optical-axis relative position data is obtained byreal measurement by a method which will be described later.

Subsequently, the positioning of the mask plate 12 and the substratewill be described with reference to FIGS. 5( a) and 5(b). As illustratedin FIG. 5( a), the substrate 10 to be printed is formed with a pair ofrecognition marks 10 m (substrate recognition marks) at diagonalpositions. In the mask plate 12 extended on the mask frame 12 a, asubstrate region 12 d corresponding to the substrate 10 is formed with apair of recognition marks 12 m (mask recognition marks) at diagonalpositions, likewise. When the substrate positioning unit 1 is driven toposition the substrate 10 with respect to the mask plate 12, a substratecenter point 10 c which is a midpoint of the two recognition marks 10 mis aligned with a mask center point 12 c which is a midpoint of the tworecognition marks 12 m. Also, a position of the substrate 10 is adjustedso that a direction of a diagonal line connecting the two recognitionmarks 10 m is matched with a direction of the diagonal line connectingthe two recognition marks 12 m.

That is, as illustrated in FIG. 5( b), the position of the substrate 10is adjusted on the basis of position detection results of therecognition marks 10 m and 12 m by the substrate recognition camera 17 aand the mask recognition camera 17 b so that positional deviations Δxand Δy between the substrate center point 10 c and the mask center point12 c in a plane, and a deviation angle α formed between the two diagonallines become as small as possible. As illustrated in FIG. 5( a), arecognition hole 12 e and a recognition hole 9 e, which are used formeasurement of an inter-optical-axis relative position, are penetratedthrough a jig mask 12A and the clamp members 9 a at the same position ina plan view, respectively. The recognition hole 12 e and the recognitionhole 9 e are used as reference marks when the above-describedinter-optical-axis relative position data is obtained by actualmeasurement (refer to FIGS. 12( a) to 12(e), and FIGS. 13( a), 13(b),and 13(c)). The recognition hole 12 e may be formed in the mask plate 12for commercial production for use as the jig mask 12A.

Subsequently, a configuration of a control system will be described withreference to FIG. 6. Referring to FIG. 6, an arithmetic processing unit40 is a CPU. The arithmetic processing unit 40 executes a variety ofoperation and processing programs stored in a program storage unit 42 ofa storage unit 41 on the basis of a variety of data stored in a datastorage unit 43, to thereby control the respective units describedbelow. As a result, screen print operation by the screen printing unit11, and a variety of processing required in association with the printoperation are executed.

In those operation and processing, a mechanism drive unit 44 iscontrolled by the arithmetic processing unit 40 to drive the substratetransport mechanism 8, the substrate positioning unit 1, the screenprinting unit 11, and the imaging unit moving mechanism 21. Further, theimaging results of the substrate recognition camera 17 a and the maskrecognition camera 17 b are subjected to recognition processing by arecognition processing unit 45, to thereby detect the positions of therecognition marks 10 m and the recognition marks 12 m of the substrate10 and the mask plate 12 in the respective processing described below.Further, the position of the reference mark in the optical axiscalibration processing, and the position of the reference point in thesurface correction data creation processing are detected. That is, therecognition processing unit 45 subjects the imaging result of themarking imaging operation to the recognition processing, to therebyconduct the mark recognition processing of detecting the positions ofthe recognition marks 10 m (substrate recognition mark) and therecognition marks 12 m (mask recognition mark).

An operation/input unit 47 is an input unit such as a keyboard or atouch panel switch, and conducts an operation command or a variety ofdata inputs for operating the device. A display unit 48 is a displaypanel such as a liquid crystal panel, and displays a guide screen at thetime of input through the operation/input unit 47 as well as a teachingscreen in the respective processing which will be described later, thatis, an operation screen when manually teaching the positions of thesubstrate 10 and the mask plate 12, which are imaged by the substraterecognition camera 17 a and the mask recognition camera 17 b, on thescreen. A teaching processing unit 46 conducts data processing for theabove-described teaching on the basis of manual input operation throughthe operation/input unit 47.

The program storage unit 42 stores a screen print execution program 42a, an optical axis calibration processing program 42 b, a surfacecorrection data creation program 42 c, a substrate positioning controlprocessing program 42 d, and a precision evaluation processing program42 e therein. Also, the data storage unit 43 stores aninter-optical-axis relative position data 43 a, a surface correctiondata 43 b, and a precision evaluation data 43 c therein. The arithmeticprocessing unit 40 executes the screen print execution program 42 a,thereby allowing the screen printing unit 11 to execute a screen printoperation. Also, the respective functions realized by executing therespective programs of the optical axis calibration processing program42 b, the surface correction data creation program 42 c, the substratepositioning control processing program 42 d, and the precisionevaluation processing program 42 e by the arithmetic processing unit 40configure an optical axis calibration processing unit, a surfacecorrection data creation processing unit, a substrate positioningcontrol unit, and a precision evaluation unit, which will be describedlater.

Hereinafter, the functions of those units will be described. First, theoptical axis calibration processing unit conducts the processing ofdetecting relative positions (refer to the relative distance D*illustrated in FIG. 4( d)) of the respective imaging optical axes a1 anda2 on the upper surface of the substrate 10 and the lower surface of themask plate 12, which are the respective imaging surfaces of the imagingoptical axes a1 and a2 of the substrate recognition camera 17 a and themask recognition camera 17 b, and outputting the detected relativepositions as the inter-optical-axis relative position data. In thisexample, the two reference marks associated with the relative positionsare imaged by the substrate recognition camera 17 a and the maskrecognition camera 17 b of the imaging unit 17, individually, to detectthe relative positions of the imaging optical axes a1 and a2. Then, thedetection of the relative positions is conducted by the teachingoperation of aligning the two imaging optical axes a1 and a2 with therecognition hole 9 e and the recognition hole 12 e by the manualoperation, individually, on the teaching screen where the two referencemarks (recognition hole 9 e and recognition hole 12 e illustrated inFIG. 5( a)) associated with the relative positions are imaged,individually. The output data is stored in the data storage unit 43 asthe inter-optical-axis relative position data 43 a. In the substratepositioning operation, a positioning error attributable to a fact that areal inter-optical-axis relative position is different from a numericalvalue on a design data is corrected by conducting a correction by usingthe inter-optical-axis relative position data 43 a.

The surface correction data creation processing unit conducts theprocessing of obtaining a position error of the imaging optical axes a1and a2 occurring on the imaging surface in the horizontal directioncaused by the move of the imaging unit 17 by the imaging unit movingmechanism 21, as a positional deviation in the horizontal directionwhich is specific to each of reference points set in an ordered arrayfor a substrate area (a glass substrate 10B held for surface correctionby the substrate positioning unit 1 in this example) on which thesubstrate 10 is held, and a mask area (a jig mask 12B installed forsurface correction on the mask frame 12 a in this example) on which themask plate 12 is installed, respectively, and outputting the obtainedposition error as surface correction data representing a localpositional deviation state in respective planes of the substrate areaand the mask area. The output data is stored in the data storage unit 43as the surface correction data 43 b. In the substrate positioningoperation, the positioning detection error by the imaging unit 17, whichis caused by a local drive error of the imaging unit moving mechanism 21can be corrected by conducting a correction by using the surfacecorrection data 43 b.

In the optical axis calibration processing, and the surface correctiondata creation processing described above, an image in which thereference marks (recognition hole 12 e, recognition hole 9 e) formed onthe jig mask (jig mask 12A illustrated in FIG. 5( a)) and the clampmembers 9 a, and reference points 10 r and 12 r set in the calibrationsubstrate and the calibration mask (glass substrate 10B and jig mask 12Billustrated in FIGS. 14( a) and 14(b)) are imaged by the substraterecognition camera 17 a and the mask recognition camera 17 b,individually, is displayed on a teaching screen in the display unit 48,and the teaching operation of aligning the imaging optical axes a1 anda2 with the reference marks and the reference points through the manualoperation, individually, is conducted.

That is, the operator conducts the teaching operation by theoperation/input unit 47 on a display screen displayed in the displayunit 48 to teach the positions of the reference marks and the referencepoints described above by the teaching processing unit 46. As a result,positions from the above-described reference marks or reference pointsare taught by the teaching processing unit 46. As a result, positions ofthe respective reference points from an origin in the optical coordinatesystem, that is, the positional deviation is detected. That is, thesurface correction data creation processing unit detects the positionaldeviation for each of the reference points through the teachingoperation of aligning the two imaging optical axes a1 and a2 with theirreference points, on the teaching screen on which the reference pointsare imaged, through the manual operation, individually.

The substrate positioning control unit controls the imaging unit 17, theimaging unit moving mechanism 21, and the recognition processing unit 45to execute the mark recognition processing of detecting the positions ofthe recognition marks 10 m and the recognition marks 12 m by the markimaging operation of imaging the recognition marks 10 m formed on thesubstrate 10 and subjecting the imaging result in the mark imagingoperation to recognition processing. Further, the substrate positioningcontrol unit controls the substrate positioning unit 1 on the basis ofthe inter-optical-axis relative position data 43 a and the surfacecorrection data 43 b stored in the data storage unit 43, and the resultsof the mark recognition processing to execute the substrate positioningoperation of positioning the substrate 10 and the mask plate 12.

The precision evaluation unit conducts the processing for evaluating thesubstrate positioning precision in the substrate positioning operation.In this embodiment, the configuration of the precision evaluationprocessing includes three kinds of processing including productionpre-start precision evaluation processing of evaluating the substratepositioning precision prior to starting the production, productionpost-start precision evaluation processing of evaluating the substratepositioning precision at an arbitrary time during productioncontinuation after starting the production, and statistical operationprocessing of statistically processing data acquired by the precisionevaluation processing to obtain a process capability index of thedevice.

First, in the production pre-start precision evaluation processing,prior to starting the production by the screen printing device, the markimaging operation, the mark recognition processing, and the substratepositioning operation described above are executed for the verificationsubstrate and the verification mask which are produced in advance forverifying the substrate positioning precision of the substrate 10 andthe mask plate 12, and each have reference points set in an orderedarray. In this example, the verification substrate and the verificationmask identical with the glass substrate 10B and the jig mask 12Bdescribed above are used. That is, the moving operation of the imagingunit 17 by the imaging unit moving mechanism 21 is corrected on thebasis of the inter-optical-axis relative position data 43 a and thesurface correction data 43 b for the verification substrate and theverification mask, and the above mark imaging operation, the markrecognition processing, and the substrate positioning operation areexecuted. Then, after the above substrate positioning operation, themoving operation of the imaging unit 17 by the imaging unit movingmechanism 21 is corrected on the inter-optical-axis relative positiondata 43 a and the surface correction data 43 b to again execute the markimaging operation and the mark recognition processing. The positioningprecision in a state before starting the production is evaluated on thebasis of the recognition result in the mark recognition processing.Then, the operation processing for the precision evaluation isrepetitively executed to confirm the repetitive positioning precision.

Then, in the production post-start precision evaluation process, afterstarting the production by the screen printing device, the mark imagingoperation, the mark recognition processing, and the substratepositioning operation described above are executed for the substrate 10and the mask plate 12 for the commercial production. That is, the movingoperation of the imaging unit 17 by the imaging unit moving mechanism 21is corrected on the basis of the inter-optical-axis relative positiondata 43 a and the surface correction data 43 b for the substrate 10 andthe mask plate 12 to execute the mark imaging operation, the markrecognition processing, and the substrate positioning operation. Then,after the substrate positioning operation, the moving operation of theimaging unit 17 by the imaging unit moving mechanism 21 is corrected onthe basis of the inter-optical-axis relative position data 43 a and thesurface correction data 43 b to execute the mark imaging operation andthe mark recognition processing. The positioning precision in a stateafter starting the production is evaluated on the basis of therecognition result in the mark recognition processing.

In this embodiment, in the above-described production post-startprecision evaluation processing, the operation processing for theprecision evaluation is repetitively executed before and after thescreen printing operation for a predetermined number of the substrates10. As a result, an influence of the execution of the screen printoperation on the substrate positioning precision can be evaluated inaddition to the repetitive confirmation of the positioning precision.

Then, in the statistic operation processing, plural pieces ofpositioning precision data acquired by repetitively executing thepositional deviation measurement in each of the production pre-startprecision evaluation processing and the production post-start precisionevaluation processing, that is, plural pairs of positional deviations Δxand Δy, and the deviation angle α illustrated in FIG. 5( b) aresubjected to statistical processing, to thereby calculate a processcapability index Cpk indicative of a precision management level in thesubstrate positioning of the device. Those positioning precision dataand the calculated process capability index Cpk are stored in the datastorage unit 43 as the precision evaluation data 43 c. That is, theabove-described precision evaluation unit has a statistical arithmeticprocessing unit that acquires the evaluation data representing thepositioning precision by a plurality of times, and subjects the pluralpieces of evaluation data to the statistical processing to calculate theprocess capability index Cpk of the substrate positioning precision inthe screen printing device. As a result, a precision level of thesubstrate positioning in the screen printing device can be alwaysquantitatively grasped.

Subsequently, a description will be given of the operation processing inthe screen printing with reference to FIG. 7 and the subsequent figures.First, a description will be given of an overall flow of the screenprinting operation processing in the screen printing device withreference to FIG. 7. First, the surface correction data creation program42 c is executed by the use of the jig mask 12A (FIG. 5( a)), to therebyexecute the optical axis calibration processing, acquire theinter-optical-axis relative position data 43 a, and store the acquireddata in the data storage unit 43 (ST1). Then, the surface correctiondata creation processing is executed on the basis of the surfacecorrection data creation program 42 c with the use of the jig mask 12B(FIG. 14( b)), acquires the surface correction data 43 b, and stores theacquired data in the data storage unit 43 (ST2). As a result, apositioning error caused by an error in the relative position of theimaging optical axes a1 and a2, and a local positioning error caused bya drive error of the imaging unit moving mechanism 21 can be correctedin the imaging of the substrate recognition camera 17 a and the maskrecognition camera 17 b.

Subsequently, the production pre-start precision evaluation processingis executed (ST3). This processing is executed for the purpose ofverifying that a desired repetitive positioning precision is ensured bythe aid of the inter-optical-axis relative position data 43 a and thesurface correction data 43 b, in the substrate positioning operationwhich is executed with the use of the substrate positioning controlprocessing program 42 d. The production pre-start precision evaluationprocessing is conducted with the use of the verification substrate andthe verification mask (glass substrate 10B and jig mask 12B in thisexample) by the user. Then, if it is verified that the desiredrepetitive positioning precision is ensured in the production pre-startprecision evaluation processing, the screen printing operation using themask plate 12 starts for the commercial production substrate 10 (ST4).

In the screen printing operation, the substrate 10 carried from anupstream side is held by the substrate positioning unit 1 (substrateholding process). Then, the recognition marks 10 m formed on thesubstrate 10, and the recognition marks 12 m formed on the mask plate 12installed on the screen printing unit 11 are imaged by the imaging unit17 having two imaging optical axes a1 and a2 whose imaging directionsare upward and downward, respectively, and which is moved in thehorizontal direction with respect to the substrate 10 and the mask plate12 by the imaging unit moving mechanism 21 (mark imaging process). Then,the imaging result in the mark imaging process is subjected to therecognition processing by the recognition processing unit 45, to therebydetect the positions of the recognition marks 10 m and the recognitionmarks 12 m (mark recognition processing process).

Then, the substrate positioning unit 1 is controlled on the basis of theposition detection results of the recognition marks 10 m and therecognition marks 12 m, to thereby position the substrate 10 to the maskplate 12 (substrate positioning process). Then, the squeegee 16 is slidon the mask plate 12 having the pattern holes 12 b formed therein towhich a paste is supplied, to thereby print the paste on the substrate10 through the pattern holes 12 b (screen printing process). Then, thescreen printing operation is repetitively executed on a plurality of thesubstrates 10.

In a process of thus continuously executing the screen printingoperation, the production post-start precision evaluation processing isexecuted (ST5). This processing is executed at given intervals with theuse of the substrate and the mask plate 12 for the real production forthe purpose of verifying that the desired repetitive positioningprecision verified in the production pre-start precision evaluationprocessing is still maintained during continuation of the production.Then, if it is confirmed that the desired repetitive positioningprecision is maintained in the production post-start precisionevaluation processing, the screen printing operation is continued (ST6).

Subsequently, the details of the respective processing executed in theabove-described overall flow will be described. First of all, a detailedflow of the optical axis calibration processing represented in (ST1) inFIG. 7 will be described with reference to FIGS. 8, 12(a) to 12(e),13(a), 13(b), and 13(c). This processing is executed prior to the markimaging process in the above-described screen printing operation. Inthis example, an optical axis calibration processing unit that detectsthe relative positions of the respective imaging optical axes a1 and a2in the horizontal direction on the substrate upper surface and the masklower surface which are the respective imaging surfaces of the imagingoptical axes a1 and a2 of the substrate recognition camera 17 a and themask recognition camera 17 b are detected by imaging two reference marksassociated with the relative positions by the imaging unit 17,individually, and outputs the detected relative positions as theinter-optical-axis relative position data 43 a (optical axis calibrationprocessing process).

First, as illustrated in FIG. 12( a), the jig mask 12A for calibrationis installed on the mask frame 12 a (ST11). As illustrated in FIG. 5(a), the jig mask 12A is formed with the recognition hole 12 e incorrespondence to the position of the recognition hole 9 e formed in thedamp member 9 a. Then, as illustrated in FIG. 12( b), the imaging unit17 is advanced (arrow c), and the recognition hole 9 e formed in theclamp member 9 a is imaged by the substrate recognition camera 17 a(ST12). Then, after the imaging unit 17 has been retreated from above ofthe substrate positioning unit 1, the clamp member 9 a is moved uptogether with the substrate lower receiving unit 7, and is brought inclose contact with the mask plate 12 (ST13). In this state, asillustrated in FIG. 12( c), the recognition hole 12 e formed in the maskplate 12 and the recognition hole 9 e formed in the damp member 9 a arepositioned by inserting a damp pin 35 through those holes (ST14).Thereafter, as illustrated in FIG. 12( d), mask damp cylinders 36 areactuated (arrow d), and the mask frame 12 a is pushed from above to fixthe mask plate 12 (ST15). As a result, the position of the recognitionhole 12 e formed in the mask plate 12 is also fixed.

Thereafter, after the damp pin 35 has been removed from the recognitionhole 12 e and the recognition hole 9 e, the damp member 9 a is moveddown together with the substrate lower receiving unit 7 (ST16). Then, asillustrated in FIG. 12( a), the imaging unit 17 is advanced, and therecognition hole 12 e is imaged by the mask recognition camera 17 b(ST17). The imaging results by the substrate recognition camera 17 a andthe mask recognition camera 17 b are subjected to the recognitionprocessing by the recognition processing unit 45, to thereby detect thepositions of the recognition hole 9 e and the recognition hole 12 e.Then, the relative positional relationship between the imaging opticalaxis a1 of the substrate recognition camera 17 a and the imaging opticalaxis a2 of the mask recognition camera 17 b is confirmed on the basis ofthe position detection result of the recognition hole 9 e and theposition detection result of the recognition hole 12 e (ST18).

FIGS. 13( a), 13(b), and 13(c) illustrate a method of acquiring theinter-optical-axis relative position data 43 a in the above-describedoptical axis calibration processing. That is, in FIG. 12( e)illustrating a state after the clamp pin has been removed, asillustrated in FIG. 13( a), the recognition hole 12 e of the mask plate12 and the recognition hole 9 e of the clamp member 9 a are in analignment state (refer to alignment line AL) in which the planepositions of the respective center points C1 and C2 are aligned witheach other.

Then, as illustrated in FIG. 13( b), the imaging point P1 of the imagingoptical axis a1 of the substrate recognition camera 17 a is matched withthe center point of the recognition hole 9 e to recognize the position.Thereafter, as illustrated in FIG. 13( c), in the alignment state inwhich the plane positions of the respective center points C1 and C2 arealigned with each other, the imaging point P2 of the imaging opticalaxis a2 of the mask recognition camera 17 b is aligned with the centerpoint of the recognition hole 12 e to recognize the position. This makesit possible to detect the relative positional relationship of therespective optical coordinate systems of the substrate recognitioncamera 17 a and the mask recognition camera 17 b, that is, thehorizontal relative positions of the imaging optical axes a1 and a2 onthe respective imaging surfaces. As a result, the position recognitionresults detected by the two individual optical coordinate systems of thesubstrate recognition camera 17 a and the mask recognition camera 17 bcan be obtained as positions in a common coordinate system. This makesit possible to correct the position detection error attributable to afault of the positional relationship between those optical coordinatesystems.

In the example of this embodiment, the recognition hole 9 e and therecognition hole 12 e respectively formed in the damp member 9 a and thejig mask 12A are used as the two reference marks, and as a method ofassociating the relative positions of those holes with each other, thereis used a method of inserting the damp pin 35 through those holes. Thosetwo reference marks may be reference marks having a configuration otherthan that in the example shown in this embodiment if a mutualrelationship of those two reference marks is associated with some means.

Subsequently, a detailed flow of the surface correction data creationprocessing shown in (ST2) of FIG. 7 will be described with reference toFIGS. 9, 14(a) and 14(b), and FIGS. 15( a), 15(b), and 15(c). Thesurface correction data creation processing is executed prior to themark imaging process in the above-described screen printing operation.In this example, a position error of the imaging optical axes a1 and a2occurring on the imaging surfaces in the horizontal direction caused bythe move of the imaging unit 17 by the imaging unit moving mechanism 21is obtained as a positional deviation in the horizontal direction whichis specific to each of reference points set in an ordered array for asubstrate area on which the substrate is held and a mask area on which amask plate is installed, respectively, and outputs the obtained positionerror as surface correction data representing a local positionaldeviation state in the respective planes of the substrate area and themask area (surface correction data creation processing process).

In the surface correction data creation processing, the glass substrate10B and the jig mask 12B illustrated in FIGS. 14( a) and 14(b) are used.As illustrated in FIG. 14( a), the glass substrate 100B has the sameouter diameter dimension as that of the substrate 10 for commercialproduct to be worked, and is provided with the same recognition marks 10m as those on the substrate 10. Further, on the glass substrate 10B, thereference points 10 r for conducting the surface correction, whichcorrects the positional deviation caused by a local drive error of theimaging unit moving mechanism 21 when the imaging unit 17 is moved bythe imaging unit moving mechanism 21 within the substrate area, are setat the respective intersections of grid lines having pitches px and py.

In the surface correction data creation, those reference points 10 r areimaged and positionally detected while the substrate recognition camera17 a is moved by the imaging unit moving mechanism 21, to thereby obtainthe surface correction data for correcting the position in the opticalcoordinate system of the substrate recognition camera 17 a and the realposition. In this example, in order to prevent the position error of thereference points 10 r unavoidably occurring in the manufacturing processof the glass substrate 10B from lessening the reliability of the surfacecorrection data, in this embodiment, in a manufacturer of the glasssubstrate 10B, the result of precisely measuring βij(x) and βij(y)representing the positional deviation error from a grid point Cij, whichis a regular position of each reference point 100 r, in advance, iscreated as a calibration data for each serial No. which is ID dataspecific to each glass substrate 10B, and attached to the glasssubstrate 10B.

FIG. 14( b) illustrates the jig mask 12B used for creating the surfacecorrection data of the mask recognition camera 17 b that recognizes themask plate 12. In the jig mask 12B, as with the recognition marks 10 mand the reference points 10 r in the glass substrate 10B shown in FIG.14( a), the recognition marks 12 m and the reference points 12 r areprovided within the substrate region 12 d indicative of a rangecorresponding to the glass substrate 10B. In the surface correction datacreation, those reference points 12 r are imaged to detect the positionthereof while the mask recognition camera 17 b is moved by the imagingunit moving mechanism 21, to thereby obtain the surface correction datafor correcting the position in the optical coordinate system of the maskrecognition camera 17 b and the real position.

As with the calibration data in the reference points 10 r on the glasssubstrate 10B, in the jig mask 12B, the calibration data is created foreach serial No. which is ID data specific to each jig mask 12B, andattached to the jig mask 12B. Then, in creating the surface correctiondata for the substrate area and the mask area, an influence of thepositional deviation errors of the reference points 10 r and 12 r on theglass substrate 10B and the jig mask 12B is removed taking thosecalibration data into account. That is, in the surface correction datacreation processing process, in any one or both of the glass substrate10B for calibration and the jig mask 12B for calibration, the surfacecorrection data is created taking into account the calibration dataobtained by measuring the positional deviations from the regularpositions of the respective reference points 10 r and 12 r in advance.

Referring to FIG. 9, the glass substrate 10B for calibration is firstheld in the substrate positioning unit 1, and the jig mask 12B forcalibration is installed (ST21). That is, the glass substrate 10B forcalibration on which the reference points are formed in the orderedarray is held in the substrate area, and the jig mask 12B forcalibration on which the reference points are formed in the orderedarray is installed in the mask area. Then, the specific measurement dataof the glass substrate 10B and the jig mask 12B, that is, thecalibration data attached to the glass substrate 10B and the jig mask12B is selected on the basis of the serial Nos. of the glass substrate10B and the jig mask 12B (ST22).

In this example, it is determined whether the serial Nos. of the glasssubstrate 10B and the jig mask 12B have already been registered, or not(ST23). In this situation, if serial Nos. have not yet been registered,the calibration data which is the specific measurement data of the glasssubstrate 10B and the jig mask 12B is read to register the serial Nos.of the glass substrate 10B and the jig mask 12B (ST24). With the aboveoperation, the teaching processing for the glass substrate 10B and thejig mask 12B is enabled.

First of all, the teaching processing on the substrate side is executed(ST25). That is, as illustrated in FIG. 15( a), the substraterecognition camera 17 a is moved above the glass substrate 10B by theimaging unit moving mechanism 21 to image a substrate front surface 10d. In this situation, as illustrated in FIG. 15( b), an imaging visualfield A of the substrate recognition camera 17 a is moved along the gridlines on which the reference points 10 r are formed (arrow f), and ateaching screen that images those reference points 10 r are displayed onthe display unit 48 (FIG. 6). As a result, the teaching screenillustrated in FIG. 15( c) is displayed on a display panel 48 a of thedisplay unit 48. In this situation, the position of the reference points10 r on the imaged screen in a state where the imaging optical axis a1is moved to the position of the reference points 10 r on the controldata, and an origin O (corresponding to the position of the imagingoptical axis a1) of the optical coordinate system do not always matcheach other due to the drive error of the imaging unit moving mechanism21, and are positionally deviated from each other by positionaldeviations δx and δy corresponding to the drive error.

In order to detect such positional deviations δx and δy, the operatorconducts the teaching operation for teaching the position of thereference points 10 r. That is, the operator operates theoperation/input unit 47 to finely move the imaging unit moving mechanism21 so that the origin O of the optical coordinate system on the teachingscreen matches the reference points 10 r on the teaching screen. As aresult, the teaching processing unit 46 detects the small amount ofmotion of the imaging unit moving mechanism 21 as the positionaldeviations δx and δy. Then, the teaching operation is executed on all ofthe reference points 10 r on the glass substrate 10B, to therebycomplete the teaching processing on the substrate side. Then, likewise,the teaching processing on the mask side is executed (ST26). In thisexample, the mask recognition camera 17 b is moved below the jig mask12B by the imaging unit moving mechanism 21, and the mask lower surfaceis imaged. As a result, as in the above description, the operatorconducts the teaching operation of teaching the position of thereference points 12 r set in a lattice arrangement on the jig mask 12B.

If the teaching processing on the substrate side and the mask side iscompleted in the above manner, the teaching result is displayed on thescreen of the display unit 48 (ST27). Then, the operator confirmswhether a numerical value of the displayed teaching result is proper, ornot (ST28). If it is determined that the numerical value of the teachingresult is not proper in (ST28), the processing of (ST25) and thesubsequent steps is repetitively executed until it is determined thatthe numerical value is proper in (ST28). Then, if it is determined thatthe teaching result is proper in (ST28), the teaching results are outputas the surface correction data 43 b of the substrate recognition camera17 a and the mask recognition camera 17 b, and stored and registered inthe data storage unit 43 (ST30). Thereafter, the glass substrate 10B andthe jig mask 12B are removed (ST31), and the teaching process forcreation of the surface correction data is completed (ST32).

Thus, when the inter-optical-axis relative position data 43 a isobtained and stored, there can be corrected a mounting positionaldeviation of the substrate recognition camera 17 a and the maskrecognition camera 17 b, and the positioning error of the substrate 10and the mask plate 12 caused by an error of the inter-optical-axisrelative distance attributable to the inclination of the imaging opticalaxis a1 or the imaging optical axis a2. Also, when the surfacecorrection data 43 b is obtained and stored, there can be corrected aposition recognition error by the substrate recognition camera 17 a orthe mask recognition camera 17 b which is caused by a local mechanicalerror of a direct operated mechanism configuring the imaging unit movingmechanism 21. Accordingly, even if the substrates 10 different in sizeare targeted, and the position of the recognition mark which is thestandard of positioning is different in each of the substrates, theposition of the recognition mark can be always detected with highprecision, and the positioning precision between the substrate 10 andthe mask plate 12 can be improved.

Subsequently, a detailed flow of the production pre-start precisionevaluation processing shown in (ST3) of FIG. 7 will be described withreference to FIG. 10. The production pre-start precision evaluationprocessing is executed for evaluating the positioning precision in thesubstrate positioning operation, in particular, the repetitivepositioning precision when repetitively executing the same operation,before starting the production of the above-described screen printingoperation.

In this example, the glass substrate 10B as the verification substrateand the jig mask 12B as the verification mask, which are prepared forverifying the positioning precision of the substrate and the mask platein advance, and have the reference points set in the ordered array, aretargeted, the moving operation of the imaging unit 17 by the imagingunit moving mechanism 21 is corrected on the basis of theinter-optical-axis relative position data 43 a and the surfacecorrection data 43 b to execute the mark imaging operation, the markrecognition processing, and the substrate positioning operation. Then,after the substrate positioning operation, the moving operation of theimaging unit 17 by the imaging unit moving mechanism 21 is corrected onthe basis of the inter-optical-axis relative position data 43 a and thesurface correction data 43 b to execute the mark imaging operation andthe mark recognition processing. The substrate positioning precision ina state before starting the production is evaluated on the basis of therecognition result in the mark recognition processing (productionpre-start precision evaluation processing process).

Referring to FIG. 10, the glass substrate 10B for precision verificationis first held in the substrate positioning unit 1, and the jig mask 12Bfor precision verification is installed on the mask frame 12 a (ST41).In this example, the glass substrate 10B and the jig mask 12B which arethe same as those used for the surface correction data creationprocessing are used for the precision verification. The specificmeasurement data of the glass substrate 10B and the jig mask 12B, thatis, the calibration data attached to the glass substrate 10B and the jigmask 12B is read (ST42).

Then, the imaging unit 17 is advanced to image the recognition marks 10m of the glass substrate 10B and the recognition marks 12 m of the jigmask 12B, respectively, and detect the positions thereof (ST43). Then,the substrate positioning operation of positioning the glass substrate10B and the jig mask 12B is executed on the basis of the amount ofpositioning correction obtained by adding the surface correction data 43b as well as the specific measurement data of the glass substrate 10Band the jig mask 12B to the position detection result (ST44). As aresult, the substrate positioning is executed so that the positionaldeviations Δx and Δy, and the deviation angle α illustrated in FIG. 5(b) become as small as possible.

Thereafter, the measurement for evaluating the substrate positioningresult in precision is conducted. That is, the imaging unit 17 is againadvanced to image the recognition mark of the glass substrate 10B andthe recognition mark of the jig mask 12B, and measure the substratepositioning precision (ST45). In this example, the substrate positioningoperation and the substrate positioning precision measurement describedabove are repetitively executed by a predetermined number of times forthe purpose of acquiring the Cpk value for confirming the devicereliability.

That is, the operation processing of (ST43) to (ST45) is repetitivelyexecuted, and it is determined whether the substrate positioningoperation and the substrate positioning precision measurement have beenrepetitively executed by the given number of times, or not, in (ST46).If it is determined that the execution has been completed in (ST46), themeasurement result is subjected to the statistical processing to acquirethe Cpk value (ST47). In this example, the Cpk value is a known indexvalue generally known as a production management technique, andcalculated for each of the positional deviations Δx, Δy, and thedeviation angle α as the positioning precision data illustrated in FIG.5( b). The Cpk value is defined by a value obtained by dividing presetstandard widths of the respective data by 6σ (σ: standard deviation)obtained for the respective measurement data.

The measurement result of the acquired Cpk value is displayed on thescreen, and it is confirmed whether the measurement result is proper, ornot (ST48), and if the determination is no, remeasurement is executed(ST49). In this case, the operation processing subsequent to (ST43) isrepetitively executed. Then, if the determination is yes in (ST48), theacquired Cpk value is output, and registered (ST50).

Thereafter, the glass substrate and the jig mask are removed (ST51), andthe production pre-start precision evaluation processing is completed(ST52).

Subsequently, a description will be given of a detailed flow of theproduction post-start precision evaluation processing shown in (ST5) ofFIG. 7 with reference to FIG. 11. The production post-start precisionevaluation processing is executed for evaluating the positioningprecision after starting the production in the above-described screenprinting operation, in particular, the repetitive positioning precisionwhen the same operation is repetitively executed on the same substrate.

In this example, the moving operation of the imaging unit 17 by theimaging unit moving mechanism 21 is corrected for the substrate 10 andthe mask plate 12 for the commercial production on the basis of theinter-optical-axis relative position data 43 a and the surfacecorrection data 43 b to execute the mark imaging operation, the markrecognition processing, and the substrate positioning operation. Then,after the substrate positioning operation, the moving operation of theimaging unit 17 by the imaging unit moving mechanism 21 is corrected onthe basis of the inter-optical-axis relative position data 43 a and thesurface correction data 43 b to execute the mark imaging operation andthe mark recognition processing. The substrate positioning precision ina state before starting the production is evaluated on the basis of therecognition result in the mark recognition processing.

Referring to FIG. 11, the number of substrates to be evaluated inprecision is set and input (ST61). The number of substrates isexperimentally set according to the degree of quality reliabilityrequired for the substrates, individually. Then, the mask plate 12 forthe commercial production is installed on the mask frame 12 a (ST62).Then, print data for executing the screen printing for the subject isread (ST63). Then, the substrate 10 for the commercial production iscarried in the device, and held by the substrate positioning unit 1(ST64). Then, the imaging unit 17 is advanced to image the recognitionmarks 10 m of the substrate 10 and the recognition marks 12 m of themask plate 12, and detect the positions thereof (ST65).

Then, the substrate positioning operation of positioning the substrateand the mask plate 12 is executed on the basis of the amount ofpositioning correction obtained by adding the inter-optical-axisrelative position data 43 a and the surface correction data 43 b to theposition detection result (ST66). Thereafter, the measurement forevaluating the substrate positioning result in precision is conducted.That is, the imaging unit 17 is again advanced to image the recognitionmark 10 m of the substrate 10 and the recognition mark 12 m of the maskplate 12, and measure the substrate positioning precision (ST67).

Thereafter, the screen printing operation is executed. That is, thesubstrate 10 is abutted against the lower surface of the mask plate 12,and the squeegee 16 is slid on the mask plate 12, to thereby execute thescreen printing operation of printing the solder cream (ST68). Then, theplate releasing operation of releasing the substrate 10 from the lowersurface of the mask plate 12 is executed (ST69). As a result, the screenprinting operation for a single substrate is completed.

Thereafter, the measurement for evaluating the substrate positioningresult in precision after the substrate positioning operation has beenexecuted is conducted. That is, the imaging unit 17 is again advanced toimage the recognition mark 10 m of the substrate 10 and the recognitionmark 12 m of the mask plate 12, and measure the substrate positioningprecision (ST70). Then, the substrate 10 after the screen printing iscarried downstream out of the substrate positioning unit 1 (ST71).

In this situation, it is determined whether the precision evaluation hasbeen completed on the set number of substrates, or not (ST72). If theevaluation has not yet been completed, the flow returns to (ST64), a newsubstrate 10 is carried in, and the same operation processing isrepetitively executed. Then, if the precision evaluation completion isconfirmed in (ST72), the measurement result is subjected to thestatistical processing to acquire the Cpk value, and display theprecision evaluation result on the display unit 48 (ST73). The Cpk valueobtained in this case is the same as that in the production pre-startprecision evaluation processing. Then, it is determined whether thedisplayed evaluation result is good, or not, by the operator (ST74). Ifit is determined that the result is good, the production is continued asit is (ST75). Then, if the evaluation result is not good, the productionis suspended (ST76), and a measure for correcting no-good isimplemented.

That is, in the production post-start precision evaluation process, themark imaging operation and the mark recognition processing are executedbefore and after the screen printing process for one substrate 10 to beevaluated. As a result, an influence of the execution of the screenprinting operation on the substrate positioning precision can beevaluated empirically.

As described above, in the screen printing according to this embodiment,prior to the mark imaging process that is executed for detecting thepositions of the recognition marks 10 m and the recognition marks 12 min the positioning of the substrate 10 and the mask plate 12, there areexecuted the optical axis calibration processing process of detectingthe horizontal relative positions of the imaging optical axes a1 and a2of the substrate recognition camera 17 a and the mask recognition camera17 b, and outputting the detected relative positions as theinter-optical-axis relative position data 43 a, and the surfacecorrection data creation processing process of detecting the localpositional deviations of the imaging optical axes a1 and a2, which arecaused by the move of the imaging unit 17 by the imaging unit movingmechanism 21, and outputting the positional deviations as the surfacecorrection data 43 b. Then, the production pre-start precisionevaluation process is executed for evaluating the positioning precisionin the substrate positioning operation with the use of the verificationsubstrate and the verification mask before the production starts.Further, the production pre-start precision evaluation process thatevaluates the substrate positioning precision in a state after theproduction starts is executed with the use of the substrate 10 and themask plate 12 for the commercial production after the production starts.

As a result, in a configuration in which the imaging unit 17 having thetwo imaging optical axes a1 and a2, which is intended to image thesubstrate 10 and the mask plate 12, an error of the relative positionbetween the imaging optical axes a1 and a2, and the position errorlocally caused by the drive error in the difference of the imaging unit17 are properly corrected to improve the substrate positioningprecision.

The present invention is based on Japanese Patent Application No.2010-234323 filed on Oct. 19, 2010, and content thereof is incorporatedherein by reference.

INDUSTRIAL APPLICABILITY

The screen printing device and the screen printing method according tothe present invention has, in a configuration in which the imaging unithaving the two imaging optical axes, which is intended to image thesubstrate and the mask plate, an error of the relative position betweenthe imaging optical axes, and the position error caused by the move ofthe imaging unit are properly corrected to improve the substratepositioning precision. The present invention is useful in the field ofthe screen printing for printing the paste such as a solder cream or aconductive paste on the substrate.

DESCRIPTION OF REFERENCE SIGNS

1 Substrate Positioning Unit

7 Substrate Lower Receiving Unit

8 Substrate Transport Mechanism

9A Clamp Member

9B Recognition Hole

10 Substrate

10 b Glass Substrate

10 r Reference Point

10 m Recognition Mark

11 Screen Printing Unit

12 Mask Plate

12A, 12B Jig Mask

12 b Pattern Hole

12 e Recognition Hole

12 r Reference Point

12 m Recognition Mark

13 Squeegee Head

16 Squeegee

17 Imaging Unit

17 a Substrate Recognition Camera

17 b Mask Recognition Camera

21 Imaging Unit Moving Mechanism

A1, A2 Imaging Optical Axis

D* Relative Distance

The invention claimed is:
 1. A screen printing device that abuts asubstrate against a mask plate in which pattern holes are formed toprint a paste, the screen printing device comprising: a substratepositioning unit that holds a substrate carried from an upstream side,and moves the substrate relatively in a horizontal direction and avertical direction to position the substrate at a given position; ascreen print unit that allows a squeegee to slide on the mask plate ontowhich the paste is supplied, to print the paste on the substrate throughthe pattern holes; an imaging unit that has two imaging optical axes ofwhich imaging directions are upward and downward, respectively, andconducts mark imaging operation of imaging a substrate recognition markand a mask recognition mark formed on the substrate and the mask plate,respectively; an imaging unit moving mechanism that moves the imagingunit in the horizontal direction with respect to the substrate and themask plate; a recognition processing unit that subjects an imagingresult in the mark imaging operation to recognition processing, therebyconducting mark recognition processing for detecting positions of thesubstrate recognition mark and the mask recognition mark; an opticalaxis calibration processing unit that detects relative positions of theimaging optical axes on a mask lower surface and a substrate uppersurface which are imaging surfaces of the two imaging optical axes,respectively, by imaging two reference marks associated with therelative positions by the imaging unit, individually, and outputs thedetected relative positions as inter-optical-axis relative positiondata; a surface correction data creation processing unit that obtains aposition error of the imaging optical axis occurring on the imagingsurfaces in the horizontal direction caused by the move of the imagingunit by the imaging unit moving mechanism, as a positional deviation inthe horizontal direction which is specific to each of reference pointsset in an ordered array for a substrate area on which the substrate isheld and a mask area on which a mask plate is installed, respectively,and outputs the obtained position error as surface correction datarepresenting a local positional deviation state in each of surfaces ofthe substrate area and the mask area; a substrate positioning controlunit that controls the imaging unit, the imaging unit moving mechanism,and the recognition processing unit so as to execute the mark imagingoperation and the mark recognition processing, and controls thesubstrate positioning unit on the basis of the inter-optical-axisrelative position data, the surface correction data, and the result ofthe mark recognition processing to execute substrate positioningoperation for positioning the substrate and the mask plate; and aprecision evaluation unit that evaluates a positioning precision of thesubstrate positioning operation, wherein the precision evaluation unitcorrects the moving operation of the imaging unit by the imaging unitmoving mechanism on the basis of the inter-optical-axis relativeposition data and the surface correction data for a commercialproduction substrate and a commercial production mask to execute themark imaging operation, the mark recognition processing, and thesubstrate positioning operation, and wherein after the substratepositioning operation, the precision evaluation unit further correctsthe moving operation of the imaging unit by the imaging unit movingmechanism on the basis of the inter-optical-axis relative position dataand the surface correction data to again execute the mark imagingoperation and the mark recognition processing, and evaluates thepositioning precision on the basis of the recognition result in the markrecognition processing.
 2. The screen printing device according to claim1, wherein the precision evaluation unit comprises a statisticalarithmetic processing unit that acquires evaluation data representingthe positioning precision by a plurality of times, and subjects pluralpieces of evaluation data to a statistical processing, therebycalculating a process capability index of the substrate positioningprecision in the screen printing device.
 3. A screen printing method inwhich a substrate is abutted against a mask plate having pattern holesformed therein to print a paste, the screen printing method comprising:holding a substrate carried from an upstream side by a substratepositioning unit; imaging a substrate recognition mark formed on thesubstrate, and a mask recognition mark formed on the mask plateinstalled in a screen printing unit by an imaging unit that has twoimaging optical axes of which imaging directions are upward anddownward, respectively, and is moved in a horizontal direction withrespect to the substrate and the mask plate by an imaging unit movingmechanism; recognizing an imaging result in the imaging of the marks bya recognition processing unit, thereby detecting positions of thesubstrate recognition mark and the mask recognition mark; positioningthe substrate to the mask plate by controlling the substrate positioningunit on the basis of the position detection results of the substraterecognition mark and the mask recognition mark; and printing a paste onthe substrate through the pattern holes by sliding a squeegee on themask plate having the pattern holes to which the paste is supplied,wherein, prior to the imaging of the marks, there are executed:detecting horizontal relative positions of the respective imagingoptical axes on a mask lower surface and a substrate upper surface whichare imaging surfaces of the two imaging optical axes, respectively, byimaging two reference marks associated with the relative positions,individually, and outputting the detected relative positions asinter-optical-axis relative position data; and obtaining a positionerror of the imaging optical axis occurring on the imaging surface inthe horizontal direction caused by the move of the imaging unit by theimaging unit moving mechanism, as a positional deviation in thehorizontal direction for each of reference points set in an orderedarray for a substrate area on which the substrate is held and a maskarea on which a mask plate is installed, respectively, and outputtingthe obtained position error as surface correction data representing alocal positional deviation state in each of surfaces of the substratearea and the mask area, wherein in a production post-start precisionevaluation that is executed for evaluating a positioning precision in asubstrate positioning operation, the moving operation of the imagingunit by the imaging unit moving mechanism is corrected on the basis ofthe inter-optical-axis relative position data and the surface correctiondata for a commercial production substrate and a commercial productionmask to execute the imaging of the marks, the recognition processing ofthe marks, and the positioning of the substrate, and wherein after thepositioning of the substrate, the moving operation of the imaging unitby the imaging unit moving mechanism is corrected on the basis of theinter-optical-axis relative position data and the surface correctiondata to again execute the imaging of the marks and the recognitionprocessing of the marks, and the positioning precision is evaluated onthe basis of the recognition result in the recognition processing of themarks.
 4. The screen printing method according to claim 3, wherein inthe precision evaluation, the mark imaging operation and the markrecognition processing are repeatedly executed before and after thescreen printing intended for one substrate.
 5. The screen printingmethod according to claim 3, wherein in the precision evaluation,evaluation data representing the positioning precision are acquired by aplurality of times, and plural pieces of evaluation data are subjectedto a statistical processing, whereby a process capability index of thesubstrate positioning precision in the screen printing device iscalculated.